This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this pilot study is to determine whether Losartan, an FDA approved vasodilator, enhances muscle tissue perfusion in older men and women. Data from this pilot study will be used as preliminary data for resubmission of Dr. Sheffield-Moore's NIH/NIA R01 Competitive renewal. We hypothesize that Losartan, a common vasodilator, can enhance muscle tissue perfusion in the elderly. The goal of this pilot project is to determine whether Losartan, an FDA approved vasodilator and an inhibitor of the renin-angiotensin-aldosterone system, can acutely stimulate muscle tissue perfusion in elderly (as measured with contrast enhanced ultrasound). Subjects will be administered 50mg of Losartan with Doppler and CEU to follow. Results from this pilot study will go a long way to convince reviewers that Losartan is capable of enhancing muscle tissue perfusion, and thus facilitating the nutritive exchange of nutrients such as amino acids.